1. Field of the Invention
The present invention relates to rotation sensing device for detecting a fine displacement of a handle and control system for use in an electrical power steering device in vehicles and a motor driving device in industrial machines.
2. Prior Art
It is well known that, in an electrical power steering device for general and industrial vehicles and a motor driving device for industrial machines, an accurate sensing of any fine displacement of a steering handle and an operating handle is absolutely needed.
Conventional rotation sensing device for detecting a fine displacement of a handle and its control system employed in a typical electrical power steering device are schematically shown in FIG. 1. This system has a known variable resistor as a rotation sensing device 10 for detecting a fine displacement of the handle(not shown), and a control unit 20 accepting input signals from the sensing device 10 and controlling a switching unit 30 with its output signals selectively to a forward running switch 31 or a backward running switch 32. Then, by this switching unit 30, an object such as a motor 40 is operated.
However, this conventional rotation sensing device and control system have the drawbacks in that they have an inferior durability and stability to vibration and external environment mainly due to the fact that they use the contact type variable resistor for its sensing device. In addition to this, the control system commits frequent malfunctions and a lot of errors in operation due to noises mixed with input signals from the sensing device.